202 J. O. HAGSTRÖM, CRITICAL RESEARCIIES ON THE POTAMOGETONS. 



P. tragillinms n. sp. 



P. lucens L. var. 8 floridanus Ar. Benn., in Graebner, Potamag., 1007, 79 & 161. 



This species differs from all the other Lucentes by the following characteristics : 

 Stem simple up to the primary spike, from which it prolongs after the B- or D-type. 

 Anatomy: epid. + one-layered pseudohp. + subepid. strands + ligular bundles + »-ond. 

 Central stele of trio-type (= P. Min.). Leaves all short, short-petioled, slightly 

 cuspidate, 7— 9-nerved with short nerve-spaces; mid-vein not much lacunous; latera] 

 nerves joining the midvein in the leaf-apex like gramineus (fig. 102, 77 — L). Denti- 

 culation extremely fugacious. Ligules lowly bicarinate, 7-nerved in the front-field. 

 The fruits I have seen are malaianus-like with dorsal keel, ventral curvature, and 

 apical rostrum as in fig. 115. 



The plant examined was gathered in Guatemala, Laguna de Ayarza, dep. Jalapa, 

 alt. 8,000 ped, 1892 by Heyde & Lux (hb. Hann.). 



P. maeropliylloides n. sp. 



Caulis metralis teres, internodiis longis, simples v. subramosus. Fdlia anguste 

 Ianceolata, caulina 20—25 cm x ±20 mm, denticulata cnspidata petiolata, petiolis 

 ±20 mm longis, typice 1 l-(13)-nervia; sine phyllopodiis; folia coriaeea non observala ,; 

 nervus medius lacunosus; spatia interner val i a rhomboidea (vide fig.). Liguloe, tenues 

 longissimoo, 80—90 mm, obtusoo bicarinatse, carinis inferne humilibus. Pedunculvs, 

 spic<f, f indus non visi. — Anatomia caulis, vide infra! — Fig. 100, A, B, C. 



Anatomy: Stem-epidermis of rather short cells, generally 2 — 3 timcs as long 

 as broad. Along the epidermis there is a one-celled strengthening layer and no or 

 few subepidermal bast bundles. Inside we meet with 1 (2) circles of bast and 

 vaseular bundles. The central axis is surroundcd by a typical ? 7 -endodcnnis and 

 besides endowed with 4 (2) median bundles and 3 (2—3) lateral ones on either sidc, 

 all with non-fused xylem canals. The lacunar part of the leaf round the central 

 \ ascular bundle is destitutc of interlacunar as well as subepidermal strands. 



The habit of this plant is much like that of P. lucens v. longijolius. Stem 

 with long internodes, simple or with rudimental branches and long-lanceolate leaves, 

 all of which are narrow and petioled. The first and second rank veins fork as the 

 figure shows. For the form of the apex and of the nerve-Bpaces I refer to the figure, too. 



At the base of evcry shoot there are two sheaths, after which follows a narrowly 

 lanceolate leaf, not as in P, Inans a ])h\llopodium, of wliith this species as it secms is 

 void, just as it is also void of the fctcenå-inclination to diminishing the bladea from 

 both ends. Only the midnei "ve portion is lacunous but lacks mechanic tissue, because 

 of which the Leaves are soft and not rigid as in /'. lucens. Ligules \cry long, the 

 ridges of abont the same height as the thickness of the ligule, thns oonsiderably lower 

 than in /'. lucene, which has the ridges 3—4 timcs as high as the thickncss of 

 the ligule (fig. IK). Ii). 



